Process for pasteurization and enzyme inactivity of fruits by electronic heating



Patented July 12, 1949 2,476,251

PROCESS FOR PASTEURIZATION AND EN- ZYME INACTIVITY OF FRUITS BY ELEC- TRONIC HEATING Theodore Lowell Swenson, Berkeley, Calii'., assignor to the United States of America as represented by the Secretary of Agriculture No Drawing. Application April 19, 1946, Serial No. 663,336

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. (3. 757) v 8 Claims.

This application is made under the actof March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described and claimed, if patented, may be manufactured and 7 sible.

This present invention differs from the prior art in that inactivation of enzymes and pasused by or for the Government of the United tcurization are performed on the whole fruit States of America for governmental purposes in situ. The enzymes and their substratum are without the payment to me of any royalty not brought into intimate contact, and air is thereon. entirely excluded. Furthermore, the inactivation The need for a process by which fresh fruit of the enzyme systems is accomplished. in a juices, especially. citrus fruit juices, could be 10 few seconds, thus disturbing equilibrium a miniprepared to hold and maintain their natural mum and permitting processing and storing in flavors has long been felt. Processes have been the original fresh condition. developed which give reasonably satisfactory When the whole fruit is brought into the high products for such fruits as grapes and apples, frequency electrostatic field in accordance with but it has been impossible by previous methods this invention, it is heated uniformly and almost to maintain in the juices of citrus fruits, espeinstantaneously to a temperature sufficient to cially oranges, the delicacy and richness of flavor inactivate the enzyme systems and complete found in the fresh fruit orin the freshly expasteurization. It is then cooled by immersion pressed juice. in ice water or in any other'convenient manner, Among the objects of this invention is the and the juice may then be expressed or other provision of fruit juices, especially those derived processes employ d by the usual methods. Inasfrom citrus fruits, such as oranges, grapefruit, much as the enzymes have been completely inacand lemons, that retain their fresh fruit flavors tivated, it is not necessary to take any special and other desirable properties for prolonged precautions for the exclusion of air, and it is periods of storage. only necessary to employ such sanitary meas- Theseobjects are attained, in accordance with ures as would ordinarily be taken to prevent this invention, by subjecting the whole fruit, bacterial contamination. before the outer coating or skin has been rup- The f ll win mpl Will ill strate the 111- tured, to the action of a high frequency electrovention in more detail: static field. This treatment is promptly fol- Whole oranges were treated in a field of high lowed by cooling the fruit and then extracting frequency electrical energy at a frequency of the juice therefrom, or subjecting it to other about 40 megacycles per second for 2 minutes. processing procedures. This preliminary treat- The internal temperature of the oranges averment results in the inactivation of the enzymes aged about 180 F. The treated fruit was next and the pasteurization of the juice in the absence immersed in ice water for 15 minutes which of air. Enzyme and bacterial activities are the reduced the temperature to about 25 C. The two principal deterioration factors, and they fruit was then halved and burred on a commerare accelerated in the presence of air. cial burring machine. The resulting juice was Although the importance of the inactivation not significantly different from the juice of unof enzymes in fruits, vegetables and their juices treated fruit in flavor and palatability. Tests may have'been recognized in the prior art, all for the inactivation of the pectin esterase showed previous methods are directed toward either 100 percent destruction in the suspended matter treatment of cut portions of fruits or vegetables of the juice from the treated oranges. by steam blanching or treatment of their ex- Other fruits and vegetables, such as grapepressed juices by de-aeration and flash pasteurfruit, limes, tomatoes, pineapples, and so forth, ization. Inevitably this permits the active enmay be similarly treated and equally effective zymes to come into intimate contact with their results are obtained, especially in the case of substratum, upon which they are free to act citrus fruits. Oranges were used because of until inactivated. The result is deterimental to their notoriously delicate flavor that is easily the taste and other desirable properties of the destroyed. The use of oranges in the above fruit juice to a degree dependent upon the time example is illustrative only. It is to be underandspeed of such action. In consequence, the stood therefore that the invention is not limited preparation of foods, such as fruit juices, espein scope by the example, but is applicable to cially citrus fruit juices, that retain the flavor any fruit or vegetable wherein it is desired to and other desirable characteristics of fresh fruit inhibit enzyme action before applying the usual processing procedures, irrespective of whether the final product is in a fresh form or in a cooked form. Thus, the invention may be applied to any fruit or vegetable including p peaches, apricots, apples, potatoes, carrots, bananas, corn, asparagus, and so forth.

Having thus described my invention, I claim:

1. The method of preparing fruit juices from whole fruit comprising first subjecting the whole raw fruit to rapid heating action in a high frequency electrostatic field for a period sufficient to pasteurize the juice and inactivate the enzymes therein but not to cook it, then promptly cooling the whole raw fruit and expressing the juice therefrom, whereby said juice will retain its fresh fruit flavor in storage for prolonged periods.

2. The method of preparing fruit juices from citrus fruit comprising first subjecting the whole raw citrus fruit to rapid heating action in a high frequency electrostatic field for a period sufllcient to pasteurize the juice and inactivate the enzymes therein but not to cook it, then promptly cooling the whole raw fruit and expressing the juice therefrom, whereby said juice will retain its fresh fruit flavor in storage for prolonged periods.

3. The method of preparing orange juice from oranges comprising first subjecting the whole raw oranges to rapid heating action in a high frequency electrostatic field for a period suflicient to pasteurize the juice and inactivate the enzymes therein, then promptly cooling the whole raw fruit and expressing the juice therefrom, whereby said juice will retain its fresh fruit flavor in storage for prolonged periods.

4. The method of preparing grapefruit juice from. grapefruit comprising first subjecting the whole raw grapefruit to rapid heating action in a high frequency electrostatic field for a period sufficient to pasteurize the juice and inactivate the enzymes therein, then promptly cooling the whole raw fruit and expressing the juice therefrom, whereby said juice will retain its fresh fruit flavor in storage for prolonged periods.

5. The method of preparing lemon juice from lemons comprising first subjecting the whole raw lemons to rapid heating action in a high fre- 4 quency electrostatic field for a period sumcient to pasteurize the juice and inactivate the enzymes therein, then promptly cooling the whole raw fruit and expressing the juice therefrom, whereby said juice will retain its fresh fruit flavor in storage for prolonged periods.

6. In the processing of citrus fruit. the steps of subjecting the whole raw citrus fruit to rapid heating action of a field of high frequency electrical energy for a period sufiicient to inactivate the enzymes therein but not to cook the fruit, followed by promptly cooling the whole raw product to halt the heating, whereby the juice in said fruit will retain its fresh fruit flavor in storage for prolonged periods.

7. The process of claim 6 in which fruit is lliggtaig for a period of about two minutes at about 8. The method of preparing orange juice comprising placing the whole raw orange in a high frequency electric field whereby it is subjected to rapid heating for a period of about two minutes at about F., to inactive the enzymes therein. followed by promptly cooling the whole raw fruit, and thereafter expressing the juice therefrom.

THEODORE LOWELL SWENSON.

REFERENCES crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Heat Treating Shell Eggs," by Barott et al., U. S. Egg and Poultry Magazine, July 1943, page 320. 

